It is well known to construct vehicle panels such as doors, hoods, deck lids etc. by stamping an outer panel and an inner panel which are then joined together by bending the flanged edge of the outer panel over a flat edge portion of the inner panel.
For example, Applicant's U.S. Pat. No. 5,150,508 issued Sep. 29, 1992 relates to a hemming machine for producing vehicle panels. The present invention is directed to an improvement to the hemming machine disclosed in U.S. Pat. No. 5,150,508 by integrating an adhesive curing system into the hemming machine to heat/cure adhesive bonded hems.
It has been recognized in the prior art that a standard flanged hem may not be sufficient to prevent the inner panel from sliding relative to the outer panel during the assembly process. Accordingly, it has been known to employ auxiliary attachment techniques to lock the panels against relative movement. For example, by applying an arc, mig, or fusion weld to tack the hemmed-over edge of the outer panel to the inner panel.
The use of adhesive bonded hems has also been proposed in the prior art. However, in order to heat/cure the heat activated adhesive, a separate machine and operation is required. In particular, the vehicle panels must first be hemmed in a hemming machine then moved to a curing station where the adhesive located in the hem is cured by a plurality of induction heaters located around the perimeter of the panels. The heating/curing process is required to "lock-up" the panels against shifting.
This type of operation suffers from the disadvantage of requiring distinct assembly processes and machines to hem and heat/cure the adhesive used in the hem. In addition, the heating can cause panel warp and other imperfections.
In summary, prior art heating/curing operations of adhesive bonded hems are performed independent of the hemming operation and machine, which can result in improperly joined panels and prolongs the overall assembly process.
Consequently, it would be desirable to provide an adhesive curing system and method for curing adhesive bonded hems in vehicle closure panels that can be incorporated into a hemming machine such that the hemming operation and heating/curing operation of the adhesive can be performed substantially simultaneously in a single machine.